184 EMBRYOLOGY OF THE LOWER VERTEBRATES oh. 



explained as a repetition of an ancestral condition in which the 

 intestine as a whole was long and spirally coiled. 



An important feature of such a spiral coiling of the gut rudiment 

 is that it would necessarily tend to bring about a twisting of the 



Fig. 105. — Dissections of young Lepidosirens of stages 32 (A), 35 (B), 36 (C), and 37 (D), 

 from the ventral side to show the modelling of the intestine. 



g.b, gall-bladder ; li, liver ; V, ventricle. 



alimentary canal just in front of the spirally coiled portion in a 

 counter-clockwise direction as seen from behind, i.e. a movement in 

 which points on the ventral side of the alimentary canal would 

 become shifted towards the right side. As already indicated such 

 a twisting of this region of the alimentary canal actually does take 



